Though most people in Casper and the rest of the country are focusing on swine flu, or the H1N1 virus, some in the area could be experiencing a different illness -- whooping cough.

Whooping cough, medically known as pertussis, is a highly contagious bacterial disease. The cough is named for the deep rattling or "whooping" sound the affected person makes when breathing in.

"It has that classic 'whoop' to it, so people will often recognize it for that," said Dr. Eric Lawrence, a family practitioner with Rocky Mountain Family Medicine. "It's very contagious once you're already coughing. It's almost guaranteed that once someone in your house has it, everyone in your house will have it."

For the first week or so, --- said, whooping cough appears like a cold, and is difficult to differentiate from other seasonal illnesses.

Often accompanied by a runny nose, a slight fever, severe coughing and shortness of breath, the upper respiratory bacterial infection can be confused for flu or, more recently, swine flu, Lawrence said.

"During that first phase, during those first seven to 10 days, with swine flu, you're seeing more fevers than that, and higher fevers," Lawrence said. "It's a little way to differentiate."

Whooping cough can also arise as a complication of the swine or seasonal flu, since the immune systems of flu patients are weakened, he said. However, it's very rare for hospitalization or death to be required for usually healthy children and adults.

Infants and children under age 6, as well as people with asthma and other breathing disorders, are at higher risk for complications from the disease.

Although Lawrence hasn't seen any cases of whooping cough yet this year, he's heard from other doctors that Montana is experiencing an issue with the infection.

Bob Harrington with the Casper-Natrona County Health Department said he hasn't received any reports of whooping cough within the past two or three weeks; however, doctors must test for whooping cough before it's required that the disease be reported to the health department. Whooping cough is one of many reportable diseases, meaning that anyone who diagnoses the disease in a clinical or laboratory setting is required to report it to the state.

"There may indeed be some [cases of swine flu] -- this is fall. There's a lot of respiratory stuff happening," Harrington said. "In my house, we're sniffling and slurping, too."

However, there's not a cause for concern, and the health department is still concentrating on swine flu as the major reason for illness so far this cold and flu season.

"Everything that causes respiratory symptoms is not necessarily flu nor pertussis," he said. "It is reoccurring and we see it from time to time, but I haven't seen any reports for at least the last few weeks."

The Centers for Disease Control recommends that infants be vaccinated against pertussis, and that adults receive a booster shot, as well. Within the last few years, the vaccine was combined with tetanus shots, so with one injection, people can be vaccinated against both diseases. It is possible to get whooping cough even after vaccination.

City reporter Pete Nickeas contributed to this report.